Audience measurement of broadcasted television and/or radio programs has been practiced for many years. Audience measurement devices typically collect two kinds of information from statistically selected homes spread across a geographic area of interest. Specifically, audience measurement devices typically collect tuning information (e.g., information indicating the content presented to the audience such as channel information, time of consumption information, program information, etc.) and people information (e.g., information about the demographics of the audience). These two types of information are gathered, recorded and combined to produce meaningful ratings data.
Typically, each monitored household is provided with a home unit such as the example home unit 10 shown in FIG. 1. The home unit 10 includes a plurality of sensors to gather tuning information. The sensors may be hardware or software based. Frequently, each sensor is designed to gather a specific type of data that may be used to identify the program being consumed at a given time. For example, a home unit 10 may include an audio code sensor 12 that monitors the audio signal of a program being consumed to detect in-band audio codes which identify the date and time of broadcast, and the channel carrying or station broadcasting the program with which the codes are associated. These codes are typically watermarks hidden in the signal by a Psycho-Acoustic Masking algorithm. Although imperceptible to the human ear, these watermarks can be picked up by an audio sensor.
The home unit 10 may also or alternatively include a video code sensor 14 to detect video codes broadcast, for example, in a vertical blanking interval of the video component of a program being consumed. Like audio codes, video codes can be any type of signal (digital, analog), or absence of a signal that may be used to identify a program being consumed, a tuned channel, and/or a broadcasting station. For example, a given television station may always place a flash of light in the upper right corner of the screen during the vertical blanking intervals of every program it broadcasts. If this code is unique to that station (e.g., ABC™) in the relevant geographic market, when the video code sensor 14 detects a flash in the upper right hand corner of a frame, the home unit 10 or central office knows that the program being viewed has been broadcast by that station (e.g., ABC™). With this information, the time of the broadcast, and a program guide, the identity of the program being viewed can be precisely obtained. Of course, other codes may alternatively be used such as markers, alphanumeric codes, tone codes, positional codes, intensity codes, data inserted into a compressed digital bitstream, data inserted into the audio , video, or ancillary data fields, the act of turning the luminance level of a pixel brighter or darker, etc.
By way of another example, the video code sensor 14 may be an Automatic Measurement Of Line-up (AMOL) decoder. An AMOL decoder reads codes embedded in a broadcast video signal outside the active video area (i.e., outside the portion of the signal that is displayed on a television receiving the signal). As is well known, the active video area starts in the 22nd line of a broadcast frame. AMOL codes are placed in the signal in lines before the active video area (e.g., in lines 19, 20 and 21). The AMOL codes identify the channel broadcasting the program containing the codes. Because the codes are embedded outside of the active video area that appears on the television, they are not visible to viewers. However, the AMOL decoder can be used to extract the codes from the received signal to identify the program being viewed.
In still another example, the video code sensor 14 may be implemented by a video watermarking sensor. Video watermarking is like audio watermarking in that a watermark is encoded into the active video area of a broadcasted signal in such a way that it can be perceived by the video watermarking sensor, but cannot be perceived by the viewers of the program.
In yet another example, the video code sensor 14 may be implemented by an on-screen display sensor. An on-screen display sensor is structured to monitor for channel numbers displayed on the television or other viewing screen. The on-screen display sensor detects such numbers, digitizes them and uses the digitized image to identify the channel number of the channel currently being viewed.
Alternatively or additionally, the home unit 10 may also be provided with an audio signature sensor 16 and/or a video signature sensor 18. An audio signature sensor 16 records one or more segments of an audio signal output in the home for comparison against a library of audio segments to determine the identity of the associated program. Similarly, a video signature sensor 18 records one or more video frames or segments of the program being viewed for comparison (either locally or remotely) against a library of video signals. A match between the recorded signature and a signature in a library gives a high degree of confidence that the program has been correctly identified. When this identity is combined with a time of broadcast and a geographical location, the station broadcasting the program can be identified.
Alternatively or additionally, the home unit 10 may be provided with a software meter 20. A software meter 20 may monitor signals decoded by a set top box, a Digital Video Recorder, an in-home Media Server, and/or other computing device as a vehicle for identifying the programs being viewed and the stations that broadcasted the same. Typically, the software meter 20 accesses an interactive program guide or other matrix identifying program carried by the datastream processed by the set top box to identify the tuned program/broadcasting station. For example, the software meter may be implemented by a digital bitstream decoder which extracts embedded codes from a digital bitstream. For example, the digital bitstream decoder may extract codes from a signal output by a set top box (STB) (e.g., it may extract codes from an audio signal sent from the STB to an AC-3 decoder).
Software meters 20 may also be used to monitor Internet traffic. For example, a software meter 20 may track and record the universal resource locators (URLs) input to a browser running on a computer or Internet appliance in order to develop ratings information concerning Internet website visitations.
A home unit 10 typically includes five or more of the above or other types of sensors 12, 14, 16, 18, 20. These sensors 12, 14, 16, 18, 20 are sometimes referred to as “data collection engines.” Like airplane engines, multiple data collection engines 12, 14, 16, 18, 20 are available so that, if one or more of these engines should fail, the remaining engines 12, 14, 16, 18, and/or 20 are still available to collect useful data.
The data gathered by the data collection engines 12, 14, 16, 18, 20 is input to a switch 22, which may be implemented by a programmed processor. The switch 22 determines which sensors or collection engines 12, 14, 16, 18, 20 are providing valid data. Because resources are limited, the switch 22 is programmed to use the data from some of the sensors 12, 14, 16, 18, 20, and ignore the data from the remaining sensors 12, 14, 16, 18, 20. In particular, the switch 22 is provided with a static set of rules which dictates the priorities to be assigned to the sensors 12, 14, 16, 18, 20. For example, the switch 22 is typically structured to prefer audio codes to audio signatures, audio signatures to video codes, video codes to video signatures, etc. Thus, if, for example, audio codes are available and the audio code sensor 12 is working, the switch 22 may process the audio codes and ignore the outputs of the other sensors 14, 16, 18, 20. If audio codes are not available and/or the audio code sensor 12 is not functioning, the switch 22 may process the audio signatures collected by the audio signature sensor 16 while discarding the outputs of the sensors 12, 14, 18 and 20. Alternatively or additionally, when faced with limited bandwidth in the communication channel 26 between the switch 22 and central office 24, the switch 22 may store some of the collected data and output it in a time division multiplexing scheme (e.g., transmit code data, then transmit signature data, then transmit code data, etc.).
The switch 22 of the home unit 10 is typically connected to a central office 24 by a communication link 26 (e.g., the Internet, the plain old telephone system, a wireless connection, etc). The central office 24 receives the data gathered by home units 10 which are scattered across a geographical area of interest and develops meaningful ratings information from the collected data.